Pages

Tuesday, January 24, 2012

Boo!

During this past year's Interagency Crab Meeting, Bob Foy (the Kodiak lab director) briefly covered all the amazing crab projects being undertaken by NMFS at the AFSC in Kodiak. One study that caught my attention over the others was a tag/dive project looking at the incidence of commercially important crab in derelict pots. An equally interesting study caught my eye at the 2012 Alaska Marine Science Symposium: it was a side scan sonar/dive survey of derelict pots in Southeast Alaska. So let's compare ghost fishing between Womens Bay off of Kodiak and around Southeast AK, and its effects on red king crab and Dungeness crab stocks!

a ghost-fishing pot with its prize: a dead blue crab

(Callinectes sapidus) from Chesapeake Bay

You may remember this post about ghost fishing in Chesapeake Bay. Ghost fishing is when gear is lost and not retrieved in the water, but still intact enough to continue catching, and killing, animals. How many crabs are being caught by derelict pots in Alaska? Let's first look at Womens Bay:

The Kodiak project was a bit longer in scale, running from 1990 to 2008. Between that time, scientists dove on 614 lost pots and found tagged red king crabs (Paralithodes camtschaticus)in or around almost 10% of those lost pots! Of the 26 tagged crabs found, 12 were dead, including 4 mature females. Hundreds of untagged crabs were spotted as well.

a derelict pot and its king crab catch

The Southeast Alaska project ran during the summers of 2009 and 2010. First researchers used side scan sonar to identify potential pots, then they dove on the sites to confirm sightings (sometimes it was just a large rock) and retrieve the derelict pots. They found 206 pots at a density of 1 - 22 pots per square kilometer (0.4 - 8.5 square miles), and up to 50% of the pots had one or more Dungeness crabs (Metacarcinus magister) depending on the area surveyed.

watch out, little crab, you're about to be Casper-fished!

So how is this phenomenon of ghost fishing affecting the crabs overall? In southeast it's estimated that 1,812 Dungies are being caught in 1,675 pots yearly, which is less than 2% of the annual commercial harvest. But in Womens Bay, it's estimated that derelict pots kill between 6 and 12% of king crab per year! Ghost fishing is not just an issue around Kodiak and Southeast; an estimated 10,000 commercial crab pots may dot the sea floor across the Gulf of Alaska and Bering Sea. That's why it's so important for commercial and recreational crab fishermen to comply with regulations, whether it calls for 18 inches of biodegradable mesh or unobstructed escape rings on the side of a pot. In the Southeast study, 91% of the retrieved pots were in compliance with an escape mechanism. (Actually, 15% of the Southeast pots were still fishing because they were so old that marine biota had overgrown any possible escape routs!)